Pupil detection is performed in line of sight detection, expression detection, and so forth. If such pupil detection is performed when illuminance is low, a “red-eye phenomenon” occurs. This red-eye phenomenon occurs, in particular, due to blood vessels of the retina being photographed when flash photography is used while the pupils are dilated in a dark location or the like. Brightness with respect to a pupil periphery image of a pupil image in which the red-eye phenomenon occurs is greater than brightness with respect to a pupil periphery image of a normal pupil image in which the red-eye phenomenon does not occur. Therefore, under conditions in which the red-eye phenomenon occurs, it is difficult to perform stable pupil detection by applying a pupil detection method whose object is a normal pupil for which the red-eye phenomenon does not occur.
In response to this problem, a pupil detection method for use when the red-eye phenomenon occurs has heretofore been proposed (see Patent Literature 1, for example). In this pupil detection method, a pupil image in which the red-eye phenomenon has occurred is detected based on color saturation and brightness of the eye region.